External steel staircases from the Westerham workshop

Access stairs to flats, annexes and offices

The usual job is a flat over a shop that needs a separate entrance, an annexe above a garage, or an office over a unit that has lost its inside stair. Many double as the emergency exit. The other regular job is replacing a rotten timber or spalling concrete stair.

Most are a straight flight to a landing outside the door. Where the rise is over 2.5 metres, or a straight flight would run too far into the yard, we add a quarter or half landing and turn it back along the wall. With no room for either, a galvanised spiral 1.6 to 2 metres across tucks into a corner. The top landing is at least as long as the stair is wide and clear of the door swing, so an outward-opening door never reaches the top step.

Materials and treads for the weather

Mild steel, hot-dip galvanised, is right for nearly every outside stair. Stainless costs more and earns it near salt air or on show. Stringers are 10 or 12mm flat plate, or parallel flange channel on longer flights. The handrail is 42.4mm tube, returned at the ends, on one side for a stair under a metre wide and both sides at a metre or more. Guarding is vertical bar spaced so a 100mm ball cannot get through through, or mesh panels where children or dogs use the stair.

For treads, open grid grating is the standard: rain, leaves and snow drop through, it grips in frost and needs the odd sweep at most. Chequer plate is solid and quieter underfoot but holds water and can ice up. Perforated plate is the middle ground for a stair at the front of a house.

Fixings, foundations and the wall

The foot of the stair sits on a base plate anchored into concrete with resin fixings, usually M12 or M16. An existing slab or path is fine if it is sound and thick enough. If it is not, we mark a concrete pad on the drawing, sized to the stair and taken down to firm ground, for your groundworker to cast before the stair arrives.

At the top, the landing fixes back to the wall with brackets and resin anchors into brick or block, kept out of the mortar joints and away from corners. A single skin of block, a timber frame or external insulation will not usually take that load, so there the landing stands on its own posts and is only tied to the wall for steadiness.

The survey settles which of these you need.

Building Regulations and planning for an outside stair

An external stair comes under Approved Document K. A private stair needs a 150 to 220mm rise and a 220 to 320mm going; one shared by flats is held to 150 to 170mm and 250 to 400mm. Guarding is 900mm on the flight and 1,100mm round the landing, which counts as a balcony. BS 6180 sets the guarding load: 0.36kN/m for one dwelling, 0.74kN/m where flats share it.

If it is also the fire escape, Approved Document B applies: doors and windows within 1.8 metres of it must be fire-resisting, and a stair over 6 metres high needs weather protection.

Planning is separate. Flats have no permitted development rights, and a landing over 300mm above ground is outside them on a house too, so most need a planning application. We supply the drawings and calculations for both.

Hot-dip galvanising and powder coating

Every outside stair goes to the galvanising plant after welding. We drill vent and drain holes in the tubes first so the zinc runs through them and coats the inside too. Dipping to BS EN ISO 1461 gives around 85 microns on the heavier sections. It comes back bright grey, dulls to a soft matt within a year and then needs nothing for decades.

If you want colour, the stair is powder coated over the zinc. The plant prepares the zinc first so the powder keys to it and does not pinhole. Anthracite and black are the usual picks; any RAL colour is possible. It costs more than galvanising alone, and if the coat is ever chipped the zinc underneath still protects the steel.

Paint alone is a maintenance job from the first winter.

Site survey, fixed quotation and installation

Send a photo of the wall and a rough height and you will have a written estimate within the working day. Then one of us comes out for a free site survey: we measure the exact rise from ground to threshold, check what the wall is built from, test the ground, look for drains and manholes in the way, note the door swing and work out how we get the stair in.

Price is set by height and width first, then by landings, tread type, guarding and powder coat. A new pad, a crane or a long carry from the road are shown as separate lines. Once you approve the drawing the quotation is fixed and only changes if the design does.

Allow a few weeks from approved drawing to fitting; the installation process is normally one day.

Straight answers on external staircases